Triggered vacuum type circuit interrupter



Jan. 13, 1970 D, R. KURT'Z ET AL 3,489,813

TRIGGERED' VACUUM TYPE CIRCUIT INTERRUPTER Filed Nov. 6. 1957 2Sheets-Sheet 2 F/QLZ.

| \V07AG Jf/vso/P I 62 I I I I l f2 l I I I I I I I g N64 I I I I I' J0-PULSE Fo/QM//VG c/RcU/r F-'lg United States Patent O 3,489,873 TRIGGEREDVACUUM TYPE CIRCUIT INTERRUPTER Donald R. Kurtz, Malvern, and Joseph C.Sofianek,

Broomall, Pa., assignors t General Electric Company, a corporation ofNew York Filed Nov. 6, 1967, Ser. No. 680,809 Int. Cl. H01h 9/30 U.S.Cl. 200-144 10 Claims ABSTRACT 0F THE DISCLOSURE A triggered vacuuminterrupter comprising relatively movable contacts and spaced-apart,stationary annular arc-runners respectively surrounding the contactswith clearance. Triggering means is provided in one of the arcr-unnersin a position spaced radially outward from its associated contact forinitiating an arc between the arc runners in a position spaced from thecontacts, after which the contacts are driven into engagement.

This invention relates to a vacuum type circuit controller and, moreparticularly, a vacuum type circuit interrupter which includestriggering means for initiating an arc when the interrupter is infully-open position.

In U.S. Patent 3,319,121-Lee, assigned to the assignee of the presentinvention, there is disclosed a vacuum type circuit interrupter thatcomprises relatively movable contacts and triggering means forinitiating an arc between the contacts when they are in a spaced-apartfully open position. After the arc is initiated, the contacts are driventogether to extinguish the arc and provide a solid metallic path throughthe interrupter for carrying the current previously carried by the arc.This is the type of closing duty that our triggered vacuum interruptermust be capable of handling.

This type of closing duty differs significantly from that imposed on theconventional vacuum type interrupter. In the conventional interrupter,closing is initiated prior to any arcing between the contacts; and anyarcing that does occur during closing is initiated only when the gap isvery short, for example, just prior to the contacts engaging or duringany contact-bouncing that occurs immediately following initialengagement. As a result, the arcing duration is very short, and there islittle chance that the contacts of a well-designed interrupter will bedamaged by the closing. But in our interrupter, arcing persists over amuch longer period, occurring during the entire closing operation, andthis increases the chance for impairment of the contacts.

An object of our invention is to reduce the chance for impairment of thecontacts of such a triggered vacuum interrupter during a closingoperation.

In carrying out our invention in one lform, we provide a first contactand a second contact movable into and out of engagement therewith. Afirst annular arc runner surrounds the first contact and is electricallyconnected thereto. A second annular arc runner surrounds the secondcontact and is electrically connected thereto but is physically spacedtherefrom by a clearance space surrounding the second contact. Theannular arc runners are mounted in generally-aligned, spaced-apartrelationship with a primary arcing gap therebetween. Mounted in one ofthe arc runners in a position located radially outward from itsassociated contact is means including a trigger gap for injecting aconcentration of charged conduction carriers into the primary gap inresponse to a predetermined signal being applied across the trigger gap,thereby causing an are to be established between the arc runners acrossthe primary gap. After the arc is established between the arc runners,the second contact is driven intoV engagement with the rst contact.

For a better understanding of the invention, reference may be had to thefollowing description taken in conjunction with the accompanyingdrawings, wherein:

FIG. l is a sectional view through a triggered vacuum interrupterembodying one form of our invention.

FIG. 2 is a schematic diagram showing an application of our triggeredvacuum interrupter.

FIG. 3 illustrates a modified form of the invention.

Referring now to FIG; l, there is shown a vacuum-type circuit controlleror interrupter comprising a highly evacuated sealed envelope 10. Thisenvelope 10 comprises a cylindrical casing 11 of insulating material anda pair of metallic end caps 12 and 13 at opposite ends of the casing 11.Suitable seals 14 are provided between the end caps and the casing 11 toprovide a vacuum-tight joint between these parts. The normal pressurewithin the envelope is lower than 10-4 mm. of mercury, so that areasonable assurance is had that the mean free path for all electronswill be longer than the potential breakdown paths in the mterrupter.

The internal insulating surfaces of the casing 11 are protected from thecondensation of arc-generated metallic vapors thereon by means of atubular metallic shield 15 suitably supported on the casing 11 andpreferably isolated from both end caps 12 and 13. This shield acts in aknown manner to intercept arc-generated metallic vapors before they canreach the casing 11.

Located within the envelope 10 is a pair of electrodes 17 and ltlshownin solid lines in FIG. 1 in their fully open posltlon. The upperelectrode 17 is a stationary electrode suitably attached to a conductiverod 17a, which at its upper end is united to the upper end cap 12. Thelower electrode 18 is referred to hereinafter as the movable electrodealthough only a portion of this lower electrode is movable. The movableportion of the lower electrode is a centrally-disposed part 20 referredto herematter as a movable contact. This contact 20 is suitably attachedto a conductive operating rod 21, which is suitably mounted for verticalmovement along the axis of the rod 21. In the dotted lines of FIG. 1,the movable contact 20 is shown in its uppermost position engaging astationary contact 24 constituting a part of the stationnary electrode17. When the contacts 20 and 24 are in this engaged position, theinterrupter is closed and current can flow therethrough via theconductive rod 17a, stationary Contact 24, movable contact 20, andconductive rod 21. Downward movement of the rod 21 separates the movablecontact 20 from the stationary contact 24 and thereby opens theinterrupter. The position of the parts when the interrupter is fullyopen is depicted with solid lines in FIG. l, where the movable contact24 has been withdrawn from the stationary contact through its fulldownward opening stroke. During a closing operation, soon to bedescribed, the movable contact 20 is driven upwardly from its solid lineposition of FIG. 1 to its dotted line position to reengage the contacts20 and 24. The operating rod 21 projects through an opening in lower endcap 13, and a flexible metallic bellows 29 provides a seal about the rod21 to allow for vertical motion of the rod without impairing the vacuuminside the envelope 10. As shown in FIG. l, the bellows 29 is secured insealed relationship at its respective opposite ends to the operating rod21 and the lower end cap 13.

The movable electrode 18 comprises a stationary arc runner 30 in theform of an annular disc surrounding the movable contact 20. Thisstationary arc runner 30 is mounted on the lower end cap 13 by means ofa tubular conductor 32 that is secured at its opposite ends to the endcap 13 and the arc runner 30. The joint between the tubular contact 32and annular arc runner 30 is located at the inner periphery of theannular arc runner for reasons which will soon be explained in moredetail. There is a relatively large clearance space 33 between themovable contact and the annular arc runner 30 about the entire outerperiphery of the movable contact 20 so as to permit free verticalmovement of the movable contact within the annular arc runner 30, aswill soon appear more clearly. The movable contact 20 and the annulararc runner 30 are electrically connected together by means of a flexiblebraid 34 located outside of the evacuated envelope 10.

The stationary electrode 17 also includes an annular arc runnersurrounding its centrally-disposed contact portion 24. This annular arcrunner, which is designated 36, is generally aligned with the other arcrunner 30 and is spaced therefrom to provide a primary arcing gap 37 ofannular configuration between the opposed faces of the arc runners.Preferably, the annular arc runner 36 is supported on the conductive rod17a by means of a radially-extending integrally-formed body portion 38that is suitably brazed at its inner periphery to the rod 17a. This bodyportion 38 has a tubular portion 38a that is joined to the arc runner 36at the inner periphery of the arc runner.

In a preferred form of our invention, the movable contact 20 is of thegeneral configuration shown and claimed in U.S. Patents 3,210,505-Porterand 3,185,799-Greenwood et al., assigned to the assignee of the presentinvention. As such, the Contact 20 is of a cup-shaped configuration andcomprises a base and a tubular wall 26 that extends from the base 25 ina direction away from the location of the stationary contact 24. Whencontact 20 is in its dotted-line closed position, engagement is madewith the stationary contact 24 along an annular surface near the outerperiphery of the contacts. As explained in the aforesaid Porter patent,the cup-shaped configuration of the movable contact 20 provides amagnetic force for driving arcs initiated on the contacts radially offthe contacts. Even when the intercontact gap is short, the tubular wall26 provides an immediately-available conductive path along which thelower terminal of the arc can run into proximity with the lower arcrunner 30 and transfer thereto.

The illustrated vacuum interrupter is a triggered vacuum interrupter andincludes trigger means for initiating an arc across the primary gap 37at a predetermined instant when the interrupter is in its fully-openposition of FIG. 1. This trigger means comprises a trigger electrodeassembly 40 associated with each arc runner. Each of these triggerelectrode assemblies 40 can be of a conventional design, such as isshown and claimed in U.S. Patent 3,087,092-Lafferty, assigned to theassignee of the present invention. These trigger electrode assembliesare identical, and therefore only one will be described. The triggerelectrode assembly associated with arc runner 30 comprises a cylindricalceramic rod 42 extending through the end cap 13 in sealed relationshipthereto and fitting into an opening in the arc runner 30. At the upperend of the ceramic rod 42 are two thin layers 44 and 46 of metal bondedto its external surface in spacedapart relationship. These two layers ofmetal constitute the electrodes of the trigger gap 47. They areseparated by a V-shaped groove 43 that extends about the circumferenceof the ceramic rod and has its walls defined by the ceramic materialitself. One of the trigger electrodes 44 is electrically connected toarc runner 30 and the other 46 is normally electrically isolated fromthe arc runner 30. The electrodes -44 and 46 can be of titaniumimpregnated with hydrogen.

As explained in the aforesaid Latferty patent, a relatively low voltagepulse applied between trigger electrodes 44 and 46 will initiate adischarge across the trigger gap 47. This discharge will evolve hydrogenfrom the trigger electrodes. This hydrogen will be immediately ionized 4by the arc and the ionized hydrogen will be rapidly propagated, orinjected, into the primary gap 37. This drastically reduces thedielectric strength of the primary gap 37 and causes it to break down inresponse to the voltage then prevailing between the arc runners 36 and30. The ionized particles that are injected into the gap are referred tohereinafter as charged conduction carriers. It will be noted that thetrigger assembly is located in a recess 39 formed in the active surfaceof the arc runner. The arc across the primary gap is typically initiatedimmediately adjacent the periphery of this recess 39.

For applying a voltage across the trigger gap, a conductive lead 48 isprovided extending through a passageway in the ceramic rod 42. At itsinner end, this lead 48 is brazed to a metallic cap 49 which is inelectrical contact with trigger electrode 46 and is hermetically sealedto the inner end of the ceramic rod. A suitable pulse forming circuit,such as indicated at 50 in FIG. 2, is connected between the lowerconductive lead 4S and the conductive rod 21 for applying a voltagepulse between these parts and hence across the trigger gap 47 at apredetermined instant.

FIG. 2 is a schematic diagram showing our interrupter applied to protectagainst overvoltages in the manner disclosed and claimed in theaforesaid Lee patent. The apparatus being protected is a seriescapacitor 60 connected in a power line 61, and the interrupter isconnected thereacross by means of conductors 62 and 64. When the voltageacross the protected apparatus 60 reaches a predetermined level, avoltage sensor 65 turns on the pulseforming circuit 50, which respondsby applying a voltage pulse to the trigger gap 47. This immediatelysparks over the trigger gap and thus produces an arc across the primarygap 37 of the interrupter. The arc establishes a low resistance patharound the protected apparatus 60 through the interrupter and conductors62 and 64, thus reducing the voltage across 60. To limit the period overwhich current ows through this arc in the low resistance path, thecontacts of the interrupter are Adriven into engagement immediatelyfollowing establishment of the arc. This is done by means of a solenoid70 connected in the low resistance path. Solenoid 70 drives theoperating rod 21 upwardly against a bias-open spring 72, thereby causingthe contacts 20 and 24 to engage. This extinguishes the arc and causesthe continuing current to flow through the solid metallic path extendingthrough the contacts. When the current through the contacts falls belowa predetermined level, the solenoid drops out and the spring 72 reopensthe contacts. On opening, the circuit controller can operate in the samemanner as a conventional vacuum interrupter, drawing an arc between thecontacts 20, 24 and forcing the arc radially outward, where it isextinguished at an early current Zero.

As pointed out in the introductory portion of this specification, theabove-described type of closing duty is more likely to impair thecontacts of the interrupter than the duty associated with a typicalcircuit-interrupter closing operation. This is the case because in thepresent type of closing duty, arcing persists for a much longer periodand is thus more likely to erode and overheat the contacts and toproduce stronger welds between the contacts when they engage. We areable to overcome this problem by initiating our arc on the arc runners30, 36 and not on the contacts 20, 24 themselves. In addition, after thearc is initiated, we force it radially outward away from the contacts20, 24 thus preventing it in most cases from reaching the contacts.Thus, the contacts, when driven into engagement, have not had a longhistory of arcing just yprior to closing impact and are thus able towithstand closing duty with less chance of impairment.

The trigger means 43-47 typically causes the arc across the main gap tobe initiated immediately adjacent the mouth of the recess 39, as waspointed out hereinabove. When the arc is in this position, there is aradiallyoutwardly acting magnetic force that drives the arc radiallyoutward away from the contacts 20, 24. This radially-outward magneticforce results from the fact that current flowing to the arc through eacharc runner enters the arc runner at its radially inner periphery andthus forms a loop-shaped path of radially-outwardly bowingconfiguration, as indicated by the dotted line C in FIG. 1. The magneticeffect of current flowing through a path of this configuration acts, ina known manner, to expand the loop and drive the arc radially outward.Current is forced to enter the arc runner at its radially innerperiphery because the tubular conductor 32 or 38a, as the case may be,through which all this current flows is joined to the arc runner at itsinner periphery.

A factor that further reduces the chance for an arc developing betweenthe contacts 20, 24 after initial establishment of an arc between thearc runners 30, 36 is that the arc voltage of the arc between the arcrunners is quite low, and there is thus little voltage available toinitiate an arc between the contacts 20, 24 while an arc is burningbetween the arc runners. This low arc voltage is a characteristic of avacuum arc, and for currents as high as several thousand amperes, arcvoltages of only 30 volts or less will typically be developed betweencopper electrodes. At much higher currents, the arc voltage typicallywill still be quite low, eg., under 100 volts.

I f, for some unusual reason, the arc established by operation of thetrigger means 40 should be initiated between the contacts 20, 24 insteadof between the arc runners 30, 36 as desired, our interrupter can stillprovide substantial protection against damage to the contacts. Thisprotection is derived from the bell-shaped configuration of the movablecontact, which, as noted above, provides a magnetic force for arctransfer to the arc-runner and an always-available arc-transfer surfaceon the exterior of the tubular portion 26 along which the arc can runand transfer to the arc runner 30. This prompt arc transfer reduces thechance that such an arc will persist on the contact surfaces for a longperiod prior to closing impact.

In a vacuum interrupter, the arc across the primary gap 37 will beextinguished at each current zero; but in the illustrated arrangementthe trigger gap will reinitiate it if a pulse is thereafter receivedfrom the pulse-forming circuit 50. In the embodiment of FIG. 2, thepulse-forming circuit 50 will continue to supply pulses to the triggergap after each current zero if the over-voltage condition persists. Eachtime the arc across the main gap is reinitiated, it behaves insubstantially the same manner as described hereinabove.

The ability of the interrupter to handle high currents without damagecan be improved by providing arc-rotating slots in the outer peripheryof the arc runners; and such slots, though not shown in the drawing, arepreferably provided. Reference may be had to U.S. Patent3,211,866--Crouch et al., assigned to the assignee of the presentinvention, for a more detailed showing of such slots. There slots causethe arc to move in a circumferentially-extending path as it approachesthe outer periphery of the arc runners. f

In the schematic showing of FIG. 2, only a single trigger gap 47 isshown; but as will be apparent from FIG. 1, a trigger gap may beprovided for each of the two main electrodes. These two trigger gaps maybe sparked over substantially simultaneously each time the primary gap37 is to be arced over; or the trigger gap associate only with the mainelectrode that happens to be the cathode at a particular instant can besparked to arc-over the primary gap 37. The presence of two trigger gapsoperated in either of these manners provides greater assurance thatoperation of the trigger gap will consistently produce arc cover of theprimary gap 37.

Although FIG. l shows the two trigger gaps 47 as being disposed insubstantially aligned relationship, we prefer to angularly offset thesetrigger gaps with respect to each other. Preferably, shown in FIG. 3,one trigger gap is disposed in a location in its associated arc-runnerdiametrically-opposed relative to the location of the other trigger gap.This widely offset relationship of the trigger gaps lessens the chancethat an arc initiated by one trigger gap will have access to and willdamage the trigger gap in the opposite electrode. The arc initiated byone trigger gap is free to move radially outward without passing nearthe other circumferentially-offset trigger gap. This offset relationshipof the trigger gaps is beneficial in protecting the trigger gaps even ina fixed electrode triggered vacuum gap, such as shown, for example, inapplication S.N. 569,944-Gallagher, filed Aug. 3, 1966, and assigned tothe assignee of the present invention.

While we have shown and described a particular embodiment of ourinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from ourinvention in its broader aspects; and we, therefore intend in theappended claims to cover all such changes and modifications as fallwithin the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A triggerable vacuum-type circuit controller comprising:

(a) a first contact and a second contact movable into and out ofengagement with said first contact,

(b) a first annular arc-runner surrounding said first contact andelectrically connected thereto,

(c) a second annular arc-runner surrounding said second contact,electrically connected thereto and physically spaced therefrom by aclearance space surrounding said second contact,

(d) means for mounting said annular arc-runners in generally-alignedspaced-apart relation with a primary arcing gap therebetween,

(e) a high evacuated envelope in which said contacts,

arc runners, and gap are located,

(f) means including a trigger gap `mounted in one of said arc-runners ina position located radially outwardly from its associated contact forinjecting a concentration of charged conduction carriers into saidprimary gap in response to a predetermined signal being applied crosssaid trigger gap, thereby causing an arc to be established between saidarc runners across said primary gap,

(g) and means for driving said second contact into engagement with saidfirst contact when said arc is established between said arc runners.

2. The circuit controller of claim 1 in combination with means forforcing the net current owing through said arc runners to the locationat which substantially all arcs are initiated therebetween by operationof said trigger gap to follow a radially-outwardly bowing path in theregion of said arc, whereby a radially-outward magnetic force isdeveloped on said arc to keep it off said contacts during a closingoperation.

3. The circuit controller of claim 1 in combination with means forcarrying current to or from an arc on said annular arc runners compisingconducting means located at the inner periphery of each of said annularrunners, said conducting means being spaced radiallyinwardly from thelocation of said trigger gap.

4. The circuit controller of claim 1 in combination with a secondtrigger gap mounted in the other of said arc runners in a positionlocated radially outward from its associated contact.

S. The circuit controller of claim 1 in which said contacts are shapedto force current flowing therethrough via an arc therebetween to followa radially-outwardly bowing loop-shaped path, thereby developing aradially-outward magnetic force on the arc.

6. The circuit controller of claim 1 in which said second contact is ofa cup-shaped configuration and comprises a base engageable with saidfirst contact and a tubular wall extending from said base in a directionaway from the location of said first contact, said second annular arcrunner surrounding said tubular wall and physically separated therefromby said clearance space.

7. The circuit controller of claim 1 in combination with a secondtrigger gap mounted in the other of said are runners in a positionlocated radially outward from its associated contact, said two triggergaps being disposed in locations widely offset from each other.

8. The circuit controller of claim 7 in which said trigger gaps aredisposed in their annular arc-runners at generally diametrically-opposedlocations.

9. The circuit controller of claim 7 in combination with means forforcing the net current owing through said are runners to the locationsat which substantially all arcs are initiated therebetween by operationof said trigger gaps to follow a radially-outwardly bowing path in theregion of said arcs.

10. A triggerable vacuum type circuit controller com prising:

(a) a pair of spaced-apart electrodes defining a primary -gaptherebetween,

(b) a pair of conductors respectively connected to said electrodes andlocated centrally of said electrodes for carrying current to or from theelectrodes when an are is present across said primary gap,

(c) said electrodes extending radially outward beyond the periphery oftheir respective conductors,

(d) means including a pair of trigger gaps mounted in the respectiveelectrodes in positions spaced radially outward from the associatedconductor for injecting a concentration of charged conduction carriersinto said primary gap in response to a predetermined signal beingapplied across either of said trigger gaps, thereby causing an arc to beestablished between said electrodes,

(e) said trigger gaps being disposed in locations widely oset from eachother circumferentially of said electrodes, and

(f) a highly evacuated envelope in which said electrodes and saidtrigger gaps are located.

References Cited UNITED STATES PATENTS 3,211,866 10/1965 Crouch et al.

3,323,002 5/1967 Laierty 315-36 FOREIGN PATENTS 616,849 3/1961 Canada.

ROBERT S. MACON, Primary Examiner U.S. Cl. X.R.

